1. Field of the Invention
The present invention relates to a light-emitting device including an element utilizing organic electroluminescence (EL) (hereinafter abbreviated to an organic EL element) between electrodes.
2. Description of the Related Art
In place of a light-emitting device such as an incandescent lamp or a fluorescent lamp which has been used for a long time, a light-emitting device including an organic EL element has been actively researched. The light-emitting device including an organic EL element has an advantage in that thickness and weight thereof can be easily reduced as compared to the thickness and weight of a conventional light-emitting device because a light-emitting material itself which is sandwiched between electrodes emits light (a so-called self-luminous element). Further, in order to utilize the advantage, the light-emitting device including an organic EL element can be attached to a curved surface.
In a conventional light-emitting device, most of the light emitted from a light-emitting material is not extracted outside but is absorbed and attenuated inside the light-emitting device because, before the light is extracted outside, light (also referred to as guided wave in the thin film mode) traveling in a plane direction while being totally reflected in the light-emitting material or an electrode and light (also referred to as guided wave in the substrate mode) traveling in the plane direction while being totally reflected in a substrate are generated.
Various methods by which the guided wave in the substrate mode and the guided wave in the thin film mode are extracted outside have been suggested, and a microlens method has been suggested as one of the methods.
The microlens method is a method by which, as disclosed in Patent Document 1, an optical structure body whose diameter is greater than that of a light-emitting portion of an organic EL element is provided so as to overlap with the organic EL element, so that the angle of light entering the optical structure body and an interface of an air layer is increased (that is, the light substantially enters perpendicularly), the guided wave in the substrate mode is less generated, and light from the organic EL element is further extracted outside, so that the amount of light emitted from the light-emitting device (also expressed as the total luminous flux of the light-emitting device) is increased.